* David Gibson (da...@gibson.dropbear.id.au) wrote:
> On Fri, Oct 03, 2014 at 06:47:43PM +0100, Dr. David Alan Gilbert (git) wrote:
> > From: "Dr. David Alan Gilbert" <dgilb...@redhat.com>
> >
> > When transmitting RAM pages, consume pages that have been queued by
> > MIG_RPCOMM_REQPAGE commands and send them ahead of normal page scanning.
> >
> > Note:
> > a) After a queued page the linear walk carries on from after the
> > unqueued page; there is a reasonable chance that the destination
> > was about to ask for other closeby pages anyway.
> >
> > b) We have to be careful of any assumptions that the page walking
> > code makes, in particular it does some short cuts on its first linear
> > walk that break as soon as we do a queued page.
> >
> > Signed-off-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
> > ---
> > arch_init.c | 149
> > ++++++++++++++++++++++++++++++++++++++++++++++++++----------
> > 1 file changed, 125 insertions(+), 24 deletions(-)
> >
> > diff --git a/arch_init.c b/arch_init.c
> > index 72f9e17..a945990 100644
> > +
> > + /*
> > + * Don't break host-page chunks up with queue items
>
> Why does this matter?
See the comment you make in a few patches time, it's about being able
to place the pages atomically on the destination.
> > + * so only unqueue if,
> > + * a) The last item came from the queue anyway
> > + * b) The last sent item was the last target-page in a host page
> > + */
> > + if (last_was_from_queue || (!last_sent_block) ||
> > + ((last_offset & (hps - 1)) == (hps - TARGET_PAGE_SIZE))) {
> > + tmpblock = ram_save_unqueue_page(ms, &tmpoffset, &bitoffset);
> > }
> > - if (offset >= block->length) {
> > - offset = 0;
> > - block = QTAILQ_NEXT(block, next);
> > - if (!block) {
> > - block = QTAILQ_FIRST(&ram_list.blocks);
> > - complete_round = true;
> > - ram_bulk_stage = false;
> > +
> > + if (tmpblock) {
> > + /* We've got a block from the postcopy queue */
> > + DPRINTF("%s: Got postcopy item '%s' offset=%zx bitoffset=%zx",
> > + __func__, tmpblock->idstr, tmpoffset, bitoffset);
> > + /* We're sending this page, and since it's postcopy nothing
> > else
> > + * will dirty it, and we must make sure it doesn't get sent
> > again.
> > + */
> > + if (!migration_bitmap_clear_dirty(bitoffset <<
> > TARGET_PAGE_BITS)) {
>
> Ugh.. that's kind of subtle. I think it would be clearer if you work
> in terms of a ram_addr_t throughout, rather than "bitoffset" whose
> meaning is not terribly obvious.
I've changed it to ram_addr_t as requested; it's slightly clearer but there
are a few places where we're dealing with the sentmap where we now need to shift
the other way. In the end ram_addr_t is really a scaled offset into those
bitmaps.
Dave
>
> --
> David Gibson | I'll have my music baroque, and my code
> david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_
> _other_
> | _way_ _around_!
> http://www.ozlabs.org/~dgibson
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
